Polarized harmonic relay and method of operating same



Apnl 7, 1964 H. E. HARTIG 3,128,357

POLARIZED HARMONIC RELAY AND METHOD OF OPERATING SAME Filed June 27, 1961 2 Sheets-Sheet 1 FIG.

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g l REED FREQUENCY INVENTOR. MAGNETIC POLE GAP---- HENRY E. HARTIG 200 20b T BY FogrgE M Ab$46rv REED To THE LEFT ATTRNEY April 7, 1964 H; E. HARTIG 3,128,357

POLARIZED HARMONIC RELAY AND METHOD OF OPERATING SAME Filed June 27, 1961 2 Sheets-Sheet 2 A Ill 0 D J O. I

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r INVENTOR. FREQUENCY HENRY E. HARTIG ATTORNEY United States Patent Ofiice 3,128,357 Patented Apr. 7., 1964 3,128,357 PDLARIZED HARMONRC RELAY AND METHGD F QPERATING SAME Henry E. Hartig, Roiahinsdale, Minn assignor to Control Corporation, a corporation of Minnesota Filed June 27, 1961, Ser. No, 120,015 16 Claims. (Ci. 200-93) This invention relates generally to polarized harmonic reed relays, and pertains more particularly to a relay of this type in which the static magnetic forces acting on the vibrating reed, which are in excess of acceptable linear forces, are substantially matched or counterbalanced for all amplitudes of reed vibration.

In a conventional type of harmonic reed relay, an elastic and magnetically permeable reed is solidly mounted at one end so as to provide a sharply resonant mechanical system when the reed is driven by an external harmonic force of magnetic character. When the frequency of the driving harmonic force is equal to the resonant frequency of the reed, it is desired that the reed vibrate much more strongly than at any other frequency. If an opposed contact is provided with which a contact on the reed engages when its vibration amplitude is sufliciently large, a local circuit may be energized, and ideally the system would as a whole constitute a relay maximally responsive only to a harmonic signal having the resonant frequency, f,, or differing only slightly therefrom in the form of a narrow band.

Attempts have been made to carry into practice the preceding ideas, but difiiculties have arisen. Instead of the ideal relay envisioned by simple theory, the behavior of the actual relay turns out to be a complicated phe nomenon which leads to performance which is far from perfect. Thus, in practice the amplitude of vibration may not be a simple function of the frequency and magnitude of the harmonic driving force, but may also depend on whether a given frequency of the driving force has been arrived at by increasing the frequency, or by decreasing the frequency. At certain points, sudden jumps of vibration amplitude occur for small increases, or decreases, in the frequency of the driving force.

One object of the present invention is to obviate or greatly minimize the foregoing disadvantages. More specifically, it is an aim of the invention to balance or compensate for the non-linear components of the magnetic forces which cause the seemingly erratic and undesired reed behavior. Stated somewhat differently, the invention has for a feature a relay possessing a reed action that is of a generally linear nature.

Another object of the invention is to provide a polarized harmonic relay having an improved sensitivity.

A further object is to provide a relay of the envisaged character possessing improved contact pressure so that relatively high local currents can be employed without damage, or with minimized damage to the contacts.

Other objects will be in part obvious and in part pointed out more in detail hereinafter.

The invention accordingly consists in the features of construction, combination of elements and arrangement of parts, and a balanced adjustment thereof, which will be exemplified in the construction hereafter set forth and the scope of the application which will be indicated in the appended claims.

In the drawings:

FIGURE 1 is a plan view of a relay depicted schematically in accordance with the teachings of the instant invention;

FIGURE 2 shows various curves with certain reed forces plotted against reed displacement both to the left and right of its normal or central position;

FIGURE 3 is a graphical presentation which portrays the kind of non-ideal response characteristics which are observed when the non-linear magnetic forces are overcompensated by the forces exerted on the reed by nonlinear contact arrangements that are too stiff;

FIGURE 4 portrays the kind of non-ideal response characteristics which are observed when the magnetic forces are under-compensated by contact arrangements that exert forces which are too weak;

FIGURE 5 shows a plurality of curves, each for a different strength of the harmonic driving force, with reed vibration amplitudes plotted against driving force frequency and pertaining to relay performance which is substantially linear, and

FIGURE 6 is a fragmentary view of a second embodiment the invention may assume, only enough structure being presented to show the difference in construction over that shown in the first embodiment of FIGURE 1.

Referring now in detail to FIGURE 1, the polarized harmonic reed relay assembly there exemplifying one embodiment of my invention has been indicated generally by the reference numeral 10. The assembly 10 includes a brass base plate 12 to which is attached a permanent magnet 14 by means of a pair of clips 16 and screws 18. In contact with the lower end of the magnet 14 is a laminated iron pole structure 20 held in place by a pair of screws 22 and in contact with the upper end of the magnet is a magnetically permeable arm 24 also afiixed to the plate 12 by screws 26. The laminated structure 20 terminates at its farther end in a bifurcated rectangular configuration 28 (this being actually part of the pole structure 20) having an air gap at 30 between the poles of said bifurcation.

Depending downwardly from the projecting end of the arm 24 is a vibratile and magnetically permeable reed 32, fabricated for instance from clock spring steel, the lower portion thereof being normally centrally positioned in the gap 30. The relay structure thus far described constitutes a magnetic path of high permeability throughout, which thus insures that the magento-motive force of the magnet 14 is optionally employed in producing magnetic flux in the air gap 30. For the purpose of later discussion, the gap 30 may be considered as being comprised of separate air gaps 30a and 3%, one to either side of the reed 32 and which are magnetically parallel in conducting the magnetic flux through the structure.

Energizing windings 34a, 34b encircle portions of the core structure 28, these windings cooperating to produce a magnetic signal flux in the series magnetic path consisting of the pole structure 28 and the air gap 30 when energized by a suitable A.-C. source, said signal flux being in additive relation to the static flux in one part of the divided gap 30, and in opposing relation in the other part of said gap. When the frequency of the source 36 is in acccordance with the resonant frequency characteristics of the reed 32, the reed will vibrate more strongly than at other source frequencies.

Carried by the reed 32 toward its free end are contacts 38a, 38b of suitable contact material such as palladium or rhodium, these contacts 38a and 38b being riveted or welded to said reed.

Inasmuch as two contacts 38a, 38b have been illustrated, the need exists for two cooperable contact units denoted generally by the reference numerals 40a and 40b, respectively. Each unit 40a and 4012 includes a block 42 of suitable insulation held fast to the brass base plate 12 by screws 44. To each insulating block 42 is affixed an L-shaped bracket 44 (when viewed from either side), the longer or horizontal leg in each instance being fixedly attached to the block by screws 46. The shorter or vertical leg of each bracket 44 supports a first leaf spring 48 through the agency of a pair of tubular rivets or bolts suflicient amplitude. The contacts 52a, 52b might be integral portions of the springs 48 provided the springs are made'of'suitable contact material.

' For a purpose soon to be made manifest, a plurality of cooperating additional leaf springs 54, 56 and 58 are employed, these springs likewise being parts of the units 40a, 40b and supported on the same rivets or bolts 50.

as are the springs 48. It will be observed that the spring 48 is the longest and that the springs 54, 56 and 58 are of progressively shorter length than the spring 48. Actually, the longest spring 48 is approximately one-third the length of the contact-carrying reed 32.

Close inspection of FIGURE 1 will show that several flat metal spacers 60, 62 and 64 of graduated length for controlling the form of the nonlinearity of each contact unit 40a, 40b are interleaved between the springs 48, 54, 56- and 58' with the longest spacer 64 being between the springs 56 and 58. Stillfurther, spacers 66 and 68 are utilized for the purpose of locating a front stop 7 and a back stop 72, respectively. Bothof these stops 70, 72

are of stiff but bendable strip metal. As can be observed from FIGURE 1, the front stop confronts that side of the spring 48 nearer the reed 32, thereby providing for limiting the spring movement of the element 48 toward the reed 32 by an easily adjustable amount depending upon to what extent the stop 70 is bent. Similarly, the back stop 72 provides easy adjustment of the overall stiffness ofthe contact units 40:1,4012 for large deflections of the spring 48; 7

From the foregoing description it can be appreciated that the contact units 40a, 40b, as their name implies, are actually units, for the various elements that comprise theseunits are held'in a stacked relation through the agency of the rivets or bolts50'.

The localized'or signaling circuit may assume a variety of forms depending upon the use to which the relay is put. Depicted in FIGURE 1 is a battery 7a, a lamp 76that-will light each time the contacts 38a, 52a or 38b, 52b make, and'a current limiting resistor 78. Also, as is conventional, a resistor 80 and capacitor 82 are connected in series across the contacts 38a, 5221 and 38b, 5217 so as to suppressthe sparking that would otherwise result when the contacts break. I

It will be of assistance at this time to consider the role played solely by the permanent'magnet 14. This magnet furnishes flux which flows over a magnetic circuit including'the arm 24, the reed 32, the air gaps 3tla, 3% to either side of the reed, the bifurcated structure 28, and the structure. 20; The flux divides equally in the air gaps 30a, 3011 when the reed 32is centrally positioned and thusthenmagnetic pull on the reed 32 balances out to zero. However, when the reed 32 is displaced to the right in FIGURE 1, the gap 30b is shortened and more flux passes through this gap than gap 30a. Consequently,

there is a magnetic pull on the reed to the right, increasing as gap 30b is shortened, Similarly, when the reed 32 is displaced to the left, gap 38a is shortened with a' concomitant increase in the pull exerted on the read as it moves to the left. V

For a more complete appreciation of the principles underlying the invention, attention is now directed to FIGURE 2. It will be observed that various curves have been plotted with reed force as the ordinate 'and reed displacement within the air gap 30 as the abscissa. The fifst curve, a'etually a straight line, to be referred to has its portions denoted by the numerals 84a, 84b and graphically represents the restoring force due to the springiness of the reed 32. The force is always in such a'direction so as to restore the reed to its central or rest position in FIGURE 1. This inherent restoring force, it will be noted, is always opposite in sign for all values of displacement with respect to the magnetic disturbing force, the numerals 86a, 86b designating the curve which represents this non-linear equilibrium-disturbing static force due to the permanent magnet 14. The non-linear character of the curve or line 86a, 8617 causes trouble, though, doing so even when the maximum equilibrium-disturbing force does not exceed the springs natural restoring force for any value of reed displacement (if this should happen the reed would not return to its central position inFIG- URE l). It has already been explained abovethat the reeds natural restoring force is represented by the straight line 84a, 84b for any amount of displacement which may be termed X. When either reed contact 38a, 38b engages its opposed relay contact 5211,5212, a; further external force is brought to bear on the reed 32 and this force has a direction contrary to that of the equilibrium-disturbing magnetic force. It is an aim of the present invention to counteract the magnetic force in whole or in part, andmore specifically it is an object to compensate for the non-linear character of this magnetic force, The vertical lines 88 hatched in betweenthe curved line 86a, 86band the straight line 89a, 8%, it can now be explained, represent the magnitudes at successive displacements of the reed 32which-would satisfactorily counteract the non-linear magnetic forces and thus produce an overall'linear characteristic. It will be understood that line' 89a, 89bis intended to represent any straight line drawn through the origin 0 which denotes the values of the net disturbing forces on the'reed 32, the counteracting forces in each instance being described by the length of a vertical line extending from a point of displacement on the curve 86a, 86b and the line 89a, 89b. A'number of such vertical lines have been drawn for various points on the curve 86a, 86b and have been collectively indicated by the reference numeral 38. It will'be remembered that the line 84a, 84b represents the natural restoring force of the reed 32. Therefore, the net're'storing force on the reed can be graphically depicted by a line tact units 40a and 40b accomplishing this task. It is the function of the springs 54, 56and '58 to do this, and

they do it by establishing the net linear relation-indicatedby the line 90a, 90b of FIGURE 2. 7

Of first importance is the observation made from FIG- URE 2 that the magnetic force on the reed 32' is not linear with respect to X.

of the pole structure 28, the average magnetic force exerted in the gap 30b is greater than when the vibration is one-half this value. Accordingly, it is to be concluded that the frequency. of resonance in the absence of compensation is depressed more for large'vibrations than for small vibrations.

When traced out in detail, the uncompensated phe! nomenon may be represented as FIGURE 4. This figure shows that as the amplitude ofthe harmonic driving force F F F F is increased, the maximum displacement amplitude X also increases and is shifted to lower frequencies. This particular figure also demonstrates that for large harmonic forces, say F the behavior is unstable. As the frequency increases, and the point d is reached, the amplitude of X suddenly jumps to 0, whereas if the frequency is now decreased, the amplitude stays Should the vibration extend from pole to pole, that is, completely across the gap 30 high until the point b is reached whereupon it suddenly decreases to a. Thus, the curves of FIGURE 4 illustrate the non-ideal response characteristics brought about by the non-linear static magnetic forces, and show that the maximum vibration amplitudes occur at successively lower frequencies as the strength of the driving force is increased to F1, F2, F3 and F4.

Obviously, for a relay to be useful it must be capable of closing a contact, such as the contact 52a, 52b in FIGURE 1, although an inductive or capacitive pickup can be utilized to achieve a desired control of an associated circuit. Each contact 52a, 52b exerts a force on the reed 32, the sense of this force being to produce an effective stiffening of the reed. If this force Were applied over the whole cycle, as is the case with the magnetic force just discussed, and if it were applied alone, that is, uninfluenced by magnetic action, then the phenomenon depicted in FIGURE 4 would be repeated, but in an opposite sense as shown in FIGURE 3. In other words, the frequency of maximum vibration would be displaced to higher frequencies as the amplitude of the applied harmonic forces were increased. Therefore, FIGURE 3 portrays the kind of non-ideal response characteristics which are observed when the non-linear magnetic forces are overcompensated by the forces exerted on the reed 32 by contact arrangements which are too stiff. It will be observed in this case that the maximum vibration amplitudes occur at successively higher frequencies as the strength of the harmonic force is increased in steps to F F F and F Prior to the teachings of the instant invention two attempts have been made to remedy the foregoing relay defects. With regard to the non-linear magnetic pull that has been referred to, this non-linear pull has been reduced by introducing an air gap in the common magnetic path. For example, if the iron leg or base 2d of FIG- URE 1 were replaced by air, the flux which passes througi the reed 32 would be substantially constant for all positions of the reed in the gap 3! As a consequence, the curve 86a, 86b would straighten out over much of its length. Thus, a linear magnetic pull as a function of X would result with the consequence that the effective spring stiffness of the reed 32 would be lessened by an amount substantially independent of vibration amplitude, and therefore, the resonant frequency would not shift with the amplitude of the harmonic driving force. Achieving linearity by this means possesses the inherent disadvantage of reducing the magnetic biasing flux in gaps 36m and 30b, assuming a permanent magnet of given size and strength. A reduction in biasing flux, though, reduces the sensitivity of the relay. The lost sensitivity could only be restored by a redesign and by increasing the length proportionately to the increase in air gap length of the permanent mag net 14.

The other prior art attempt concerns the disturbing external force introduced by the interaction of the reed 32 with a cooperating contact. This eifort has prompted the mounting of the cooperating contact on a spring having a very small stiffness. But this attempted solution carries with it the disadvantage of producing low contact pressures between the contacts with an accompanying reduction in the current carrying capacity of the contacts, and in present practice the spring which bears the cooperating contact is usually made too stiif in order to escape the consequences of low contact pressures. Frequently, the disadvantages just recited are regarded as inherent with no remedy and therefore to be endured.

Instead of employing the above-mentioned air gap or relying on a highly yieldable or resilient contact mounting, the present invention matches or balances the magnetic forces with the array of additional springs 54, 56 and 58, as stated. By making these springs 54, 56 and 58 all shorter than the reed 32, the basic vibrating frequency of the reed 32 is avoided. While the compensating force for clarity of exposition is shown as being increased in discrete steps, nonetheless a good approximation to perfect counterbalance is achieved thereby, as well as by a compound spring in which the elements are in contact with each other and the overall effect is that of a linear reed.

It has been found that in practice it is not necessary to equalize the magnetic departure from linearity for each direction of reed movement from center where but one pair of contacts are utilized, for the inertia of the reed makes it possible to equalize both the to and fro motion by means of the single set of springs of substantially double strength which accomplishes an overall dynamic equalization.

A clean contact break, as well as means for adjusting the contact spacing, is achieved through the agency of the stop 76, for this stop prevents the spring 48 and its contact 52a or 52b from following the reed 32 and its contact 38a or 3311 beyond the previously established correct contact spacing point.

A second embodiment for carrying the teachings of the invention into effect is pictured fragmentarily in FIGURE 6 and has been generally indicated by the numeral 110. Like reference numerals have been used to designate like parts wherever there is identity. However, the contact unit a (only one being shown) is different from the units dda, 49b to the extent that the leaf spring 148 corresponding to the earlier-described spring 48 rollingly engages a spring 154 on an increasingly shorter radius because of the curvature imparted to the free end of the element 154. The leaf spring 154 in turn engages the leaf spring 156 on a diminishing radius due to its curved end.

As has been herein pointed out in connection with the embodiment of FIGURE 6, only one contact unit Mild has been illustrated. This unit 140a appears at the side of the reed $2 nearer the portion of the pole structure 23 cooperating with the free end of the reed 32. to form the air gap 3ila. It will be understood that the contact unit 1 56a could be oriented or mounted on the farther side of the reed 32 in FIGURE 6 with respect to that portion of the pole structure 23 that has been shown. Under these conditions contact engagement would be effected as the free end of the reed 32 moves to the right in FIGURE 6, that is when gap 30a is increasing. Also, it will be obvious that two contact units 14% can be employed, one to either side of the reed 32, thereby corresponding to the physical layout depicted in FIGURE 1.

With the content of the preceding paragraph in mind, it Will be further appreciated that either one of the contact units 49a or 40b appearing in FIGURE 1 might be employed with the pole structure 28 that has been presented. It will be further understood that a single unit 40a or 4% might be utilized in conjunction with either air gap Stla or Silb. As a specific illustration, the righthand section of the pole structure configuration labeled 28 might be omitted, thereby using only that portion of the pole structure helping to form the gap 30a. In such a situation, either the contact unit 40a or 40b might be used rather than the pair that has been shown. Thus, if the unit 40a is selected, it would be considered to be at the side of the reed nearer the portion of the pole structure cooperating with the free end of the reed 32 to provide the air gap Sila, whereas if the unit 40b is selected, then it would be deemed to reside at the farther side of the reed with respect to the left portion of the rectangular end 28 of the pole structure 20.

Having described both of the exemplary embodiments illustrated in FIGURES 1 and 6 it will now be better appreciated that a further desirable and important property of a sheaf of springs, such as those that have been described, is the increase in the unrecoverable losses due to friction between the leaves. This has the effect of increasing the energy losses in the vibrating system within the band of width A) shown in FIGURE 5 and thus reducing excessively large amplitudes of vibration which are considerably beyond what is necessary to close the relay contacts. The resonant frequency in FIGURE has'been designated as f Since many changes could be made in the'above construction and many apparently widely different embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description. or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be. understood that the language used in the following claims is intended to cover all of the generic and specific featuresof the invention herein described and all statements of. the scope of the invention which, as a matter of language, might be said to fall therebetween.

What is claimed:

1. A polarized harmonic relay comprising a permanent magnet, magnetically permeable means including a pole structure and a vibratile reed having a free end spaced from a portion of said pole structure and forming therewith an air gap through which the magnetic fiux emanating from the permanent magnet passes thus completing a magnetic circuit, said reed having a section providing a first electrical contact on one side thereof, a second electrical contact disposed adjacent said one side in a normally spaced relationship with the first electrical contact and engageable by said first contact when thereed vibrates at a sufficient amplitude, electromagnetic means for inducing said reed to vibrate over a particular frequency range in said gap, and means acting against said second electrical contact to substantially counteract the non-linear excess of the magnetic forces acting on said reed upon engagement of said first contact with said second contact.

2. A polarized harmonic relay in accordance with claim 1 in which said first and second contacts are oriented with respect to the side of the reed nearer said pole structure portion.

3. A polarized harmonic relay in acordance with claim 1 in which said first and second contacts are oriented with respect to the side of the reed farther from said pole structure portion.

4. A polarized harmonic relay comprising a permanent magnet, magnetically permeable means associated with said permanent magnet for forming a flux air gap, said magnetically permeable means including a vibratile reed forming a part of said magnetically permeable means and having a portion thereof normally centrally disposed in said air gap and having a section thereof providing a first electrical contact, a second electrical contact disposed in a normally spaced relationship with the first electrical contact and engageable by said first contact when the reed vibrates at a sufiicient amplitude, electromagnetic means for inducing said reed to vibrate over a particular frequency range within said gap, and nonlinear spring means acting against said second electrical contact to counteract substantially the non-linear excess of the magnetic forces actingon said reed upon engagement of said first contact with said second contact.

5. A polarized harmonic relay comprising a permanent magnet, magnetically permeable means associated with said permanent magnet for forming a fiuxair gap, said magnetically permeable means including a vibratile reed forming a part of said magnetically permeable means and having a portion thereof normally centrally disposed in said gap and having a section thereof providing a first electrical contact, a second electrical contact in the form of a leaf spring anchored at one end so as to dispose its free end in a normally spaced relationship with the first electrical contact'and engagea'ole by said first contact when the reedvibrates at a sufficient amplitude, electromagnetic means for inducing said reed to vibrate over a particular frequency range within said gap, and

additional leaf springs of successively shorter length than said contact leaf spring anchored atone end so as to dispose the free-end of the longest additional spring forengagement by the free end of said contact leaf spring and the free end of the next longest additional spring for engagement by the free end of said longest additional spring with the remainder of said successive springs being similarly engageable for compensating in discrete stepsthe non-linear magnetic forces acting on said reed during engagement of said contacts, said additional leaf springs being located at the remote side of said leaf spring contact from said reed.

6. A polarized harmonic relay in accordance with claim 5 including a spacing element between each adjacent pair of leaf springs.

7. A polarized harmonic relay in accordance with claim 6 in which said spacing elements are of different.

engths, the longest spacing element being betwe'en the shortest pair of leaf springs.

8. A polarized harmonic relay in accordance with claim 5 in which the free ends of said additional springs have a curvature extending away from said first-mew tioned leaf spring. 7

9. A polarized harmonic relay comprising a permanent magnet, magnetically permeable means'associated with said permanent magnet for forming a flux air gap, a vibratile reed forming a part of said magnetically permeable means and having a portion thereof normally centrally disposed in said gap and having a section thereof providing a first electrical contact, second and third electrical contacts disposed in a normally spaced relationship with the first electrical contact and engageable by said first contact when the reed vibrates at a sufficient amplitude, electromagnetic means for inducing said reed to vibrate over a particular frequency range Within said gap, and means cooperating with said second and third electrical contacts to counteract substantially the nonlinear excess of the magnetic forces acting on said reed upon engagement of said first contact with either the said second contact or the third contact;

10. A method of operating a polarized harmonic relay having a permanent magnet, magnetically permeable means associated with said permanent magnet for forming a flux air gap, at vibratile reed contact forming a part of said magnetically permeable means, a contact engageable by said reed contact and electromagnetic means for causing said reed contact to vibrate sufiiciently to cause engagement of said reed contact with said second contact, the method comprising the step of applying a reaction force to said second contact which substantially balances the non-linear excess of the magnetic forces acting on said reed during contact engagement.

11. The method of operating a polarized harmonic relay in accordance with claim 10 in which the balancingforce is applied in discrete increments.

12. A polarized harmonic relay comprising a permanent magnet, magnetically permeable means associated with said permanent magnet for forming a flux air gap, said magnetically permeable means including a vibratile reed forming a part of said magnetically permeable means and having a portion thereof normally centrally disposed in said gap and having a section thereof providing a first electrical contact, a second electrical contact in the form of a leaf spring anchored at one. end so as to dispose its free end in a normally spaced relationship with the first electrical contact and engageable by said first.

. gages the additional springnearest thereto and saidnear est additional spring in turn rollingly engages the additional spring next to it.

13. A polarized harmonic relay comprising a permanent magnet, magnetically permeable means including a pole structure and a vibratile reed having a free end spaced from a portion of said pole structure and forming therewith an air gap through which the magnetic flux emanating from the permanent magnet passes thus completing a magnetic circuit, electromagnetic means for inducing said reed to vibrate over a particular frequency range in said gap, and means to substantially counteract the non-linear excess of the static magnetic forces acting on said reed.

14. A polarized harmonic relay in accordance with claim 13 in which said last-mentioned means becomes effective when said reed vibrates with a predetermined amplitude.

15. A polarized harmonic relay in accordance with claim 14 in which said last-mentioned means includes a spring having a contact carried thereon which is engageable by said reed at said predetermined amplitude.

16. A method of operating a polarized harmonic relay having a permanent magnet, magnetically permeable means associated with said permanent magnet for forming a flux air gap, at vibratile reed forming a part of said magnetically permeable means, and electromagnetic means for causing said reed to vibrate, the method comprising the step of applying a reaction force to said reed which substantially balances the non-linear excess of the magnetic forces acting on said reed during said vibration.

References Cited in the file of this patent UNITED STATES PATENTS 

13. A POLARIZED HARMONIC RELAY COMPRISING A PERMANENT MAGNET, MAGNETICALLY PERMEABLE MEANS INCLUDING A POLE STRUCTURE AND A VIBRATILE REED HAVING A FREE END SPACED FROM A PORTION OF SAID POLE STRUCTURE AND FORMING THEREWITH AN AIR GAP THROUGH WHICH THE MAGNETIC FLUX EMANATING FROM THE PERMANENT MAGNET PASSES THUS COMPLETING A MAGNETIC CIRCUIT, ELECTROMAGNETIC MEANS FOR INDUCING SAID REED TO VIBRATE OVER A PARTICULAR FREQUENCY RANGE IN SAID GAP, AND MEANS TO SUBSTANTIALLY COUNTERACT THE NON-LINEAR EXCESS OF THE STATIC MAGNETIC FORCES ACTING ON SAID REED. 